LCA of heavy metals leaching from landfilled sewage sludge ash

Quantities of sewage sludge that are thermally treated (mostly incinerated) are increasing, resulting in growing quantities of sewage sludge ash (SSA) which also requires further management. Despite its potential as a resource, it is still largely landfilled. Considering the presence of potentially toxic and hazardous heavy metals in SSA, this paper analyzes how the change in the leaching concentrations of the selected heavy metals from landfilled SSA impacts the environment (air, water, and soil) by the means of LCA. When considering human toxicity potential as impact category, dominant impacts were due to emissions into the air, primarily caused by leaching of selenium and somewhat less cadmium, mercury and nickel. Mercury had a dominant impact when considering the terrestrial ecotoxicity potential impact. In the SSAs obtained from Croatian sludge, molybdenum leaching, along with selenium and mercury, showed a dominant impact. Therefore, due to the high variability of trace elements, detailed analysis of different SSAs is needed

Use of sludge generated at WWTP in the production of cement mortar and concrete

U radu je opisana problematika vezana uz generiranje i zbrinjavanje mulja s UPOV-a (uređaja za pročišćavanje otpadnih voda) u Hrvatskoj. Poseban osvrt je dan na mogućnost i opravdanost korištenja pepela dobivenog spaljivanjem mulja. Naglasak je stavljen na ugradnju pepela u betonskoj industriji, pri proizvodnji cementnog morta i betona. U radu su opisani rezultati dosada provedenih istraživanja u okviru svjetske prakse, s primarnim osvrtom na utjecaj ugradnje pepela na karakteristike cementnog morta i betona.Problems relating to disposal of sludge accumulating at waste-water treatment plants (WWTP) in Croatia are described in the paper. The possibility and adequacy of using ash obtained through incineration of sludge is considered. A special emphasis is placed on the significance of ash in concrete industry during production of cement mortar and concrete. Results of worldwide research conducted so far are described, with indications about the ways in which ash use influences properties of cement mortar and concrete

Analysis of Sewage Sludge Disposal Routes – Varazdin and Medimurje County

The aim of this paper is to analyse sewage sludge production at the level of Medimurje and Varazdin counties with economic analysis of acceptable technical/technological solutions for sludge management routes. The topic is very broad, so the focus was placed on four variants of sludge disposal, which were determined by preliminary analysis to be the most applicable for the area in question. These are: 1) disposal of sewage sludge in agriculture, 2) incineration of sludge in a central mono-incinerator, 3) composting for the area of Varazdin County and at the same time use of sludge reed beds for the area of Medimurje County, and 4) export of sludge outside the state borders. Based on the analysis carried out for the described four variants, sludge incineration in a regional mono-incinerator turned out as the economically most advantageous solution, while the variant that includes disposal of sludge in agriculture has showed as the most expensive one. The last one also showed the largest range of costs uncertainties, but the mentioned facts are greatly influenced by unfavourable legislation, the changes of which in a more rational direction would greatly contribute to the greater competitiveness of this variant. Overall, taking into account the lowest cost and uncertainties in the predicted unit costs, the sludge composting in the Varazdin County and the construction of a reed beds for the Medimurje County, turned out to be the optimal variant. This solution is also the one that was ultimately adopted in practice

Comparison of different methods for expressing water losses with a review of their practical implementation in Croatia

U današnje se vrijeme u svijetu koriste različiti načini iskazivanja vodnih gubitaka u vodoopskrbnim sustavima. Najčešće je iskazivanje postotnog udjela u odnosu na zahvaćene količine, zatim izračun stvarnih i prividnih gubitaka u sklopu standardne bilance vode i izračun ILI (eng. Infrastructure Leackage Indeks; hrv. Infrastrukturni indeks curenja) pokazatelja sukladno IWA (eng. International Water Association) metodologiji. ILI pokazatelj predstavlja odnos stvarnih i neizbježnih količina vodnih gubitaka na razini jedne godine. U radu je dan kritički osvrt na pouzdanost ILI pokazatelja pri analizi vodnih gubitaka. Na konkretnim primjerima je dokazano da na temelju ILI pokazatelja nije pouzdano donositi konkretne zaključke o stanju vodnih gubitaka, kao i o definiranju mjera unaprjeđenja cjelovitih sustava ili pojedinih DMA zona (eng. District Metering Area; hrv. Izdvojena mjerena zona). U analizi vodnih gubitaka se osim izračuna ILI pokazatelja koriste i različiti načini iskazivanja i vrednovanja vodnih gubitaka (l/(priključak∙dan), m3/(km cjevovoda∙dan), l/(priključak∙dan∙mVS), m3/(km cjevovoda∙dan∙mVS), HRK/godina i dr.). S ciljem iznalaženja što jednostavnijeg i pouzdanijeg načina iskazivanja vodnih gubitaka, u ovom su radu, na konkretnih pet primjera vodoopskrbnih sustava u Hrvatskoj, analizirani odnosi različitih načina iskazivanja vodnih gubitaka. Zaključuje se da je najpraktičnije i najučinkovitije provođenje ekonomskih analiza vodnih gubitaka s izražavanjem vodnih gubitaka u HRK/godina, kako za sustav u cjelini, tako i za svaku DMA zonu posebno.There are different methods for expressing water losses in water supply systems, which are presently used in the world. Water losses are most frequently expressed as a percentage of abstracted water quantity, a calculation of real and apparent losses as part of the standard water balance and calculation of the Infrastructure Leakage Index (ILI) according to the International Water Association (IWA) methodology. The ILI presents the relation between the real and unavoidable annual water losses. The paper offers a critical review of the reliability of the ILI in the analysis of water losses. By using specific examples, the paper proves that it is not reliable to draw concrete conclusions about the state of water losses or to define measures for improving integrated systems or individual district metering areas (DMAs) based on the ILI. In addition to the ILI calculation, numerous other methods of expressing and assessing water losses are also used, such as l/(connection per day), m3/(km pipeline per day), l/(connection per day mWC), m3/(km pipeline per day mWC), HRK/year, etc. In order to find the simplest and most reliable method for expressing water losses, this paper analyses relations between different methods for expressing water losses on five specific water supply systems in Croatia. It has been concluded that the most practical and efficient performance of economic analyses of water losses is when water losses are expressed in HRK/year, both for the system as a whole and separately for each individual DMA

Pilot project – recycling sludge from wastewater treatment plants in concrete products used in water managment

S obzirom na pozitivne rezultate laboratorijskih ispitivanja mogućnosti korištenja pepela dobivenog spaljivanjem mulja s uređaja za pročišćavanje otpadnih voda (UPOV) kao zamjene za cement, javila se potreba za daljnjim ispitivanjima u proizvodnji betonskih proizvoda u stvarnoj veličini. Pilot projekt rezultat je suradnje Građevinskog fakulteta Sveučiliša u Zagrebu i tvrtke Beton Lučko d.o.o. Pepeo dobiven spaljivanjem mulja u kontroliranim laboratorijskim uvjetima korišten je kao zamjena za 10 % cementa u šesterokutnim prizmama s direktnom primjenom u području vodnog gospodarstva. Na ovaj se način direktno zatvara krug u ostvarenju temeljnih postavki cirkularne ekonomije, budući da se pepeo koji nastaje kao nusproizvod spaljivanjem mulja generiranog pročišćavanjem otpadnih voda primjenjuje u betonskim prozvodima korištenim, između ostalog, i u izgradnji objekata vodnog gospodarstva. U radu su dani kemijski sastavi dobivenih pepela, potencijalni utjecaji na okoliš ispitivani kroz izluživanje, iz pepela i iz betona s ugrađenim pepelom te rezultati ispitivanja tehničkih zahtjeva za gotove betonske proizvode prema normama definiranim zahtjevima i ustaljenoj praksi u partnerskoj tvrtki.Considering the positive results of a laboratory testing of potential uses of ash obtained by sludge incineration from wastewater treatment plants (WWTPs) as cement replacement, the need arose for further testing of the production of concrete products in actual size. The pilot project was a result of the cooperation between the Faculty of Civil Engineering of the Zagreb University and the company Beton Lučko d.o.o. The ash obtained by sludge incineration in controlled laboratory conditions was used as a replacement for 10 % of cement in hexagonal prisms that are directly used in water management. In this manner, the closed circle meant the achievement of the basic principles of circular economy, since the ash generated as a byproduct of sludge incineration from wastewater treatment is used in concrete products utilized, among others, in the construction of water management facilities. The paper contains the chemical compositions of the obtained ashes, potential environmental imapcts tested through leaching from ash and concrete containing ash as well as the test results of technical requirements for finished concrete products according to the standards and established practice in the partner company

Der Einfluss der Pandemie im Jahr 2020 auf die Ergebnisse der Wasserbedarfsanalyse und die nachfolgende Bestimmung der Abwassermengen und Kapazitäten von Abwasserkläranlagen

S ciljem suzbijanja globalne pandemije bolesti COVID-19 tijekom 2020. godine uvedene su stroge mjere koje su ograničavale brojne aktivnosti, djelatnosti i kretanje stanovništva na razini cijelog Svijeta pa tako i Hrvatske. U ovom radu analiziran je utjecaj uvedenih ograničenja na kretanje potrošnje vode po pojedinim kategorijama potrošača (kućanstva, privreda) na temelju podataka prikupljenih za 17 isporučitelja vodnih usluga na području Republike Hrvatske. Pritom su podjednako zastupljeni podaci za kontinentalni (ne-turistički) i primorski (turistički orijentiran) dio teritorija. Provedena je analiza potrošnje vode u 2020. godini u odnosu na prosječne vrijednosti potrošnje u prethodnom petogodišnjem periodu. Detektirane su promjene u odnosu na udio pojedine kategorije u ukupnoj potrošnji te su dani zaključci i preporuke o potrebi kritičkog sagledavanja podataka za 2020. godinu prilikom izrade projekcija u sklopu analize potreba za vodom. Na pokaznom primjeru demonstriran je i utjecaj promjena u potrošnji vode 2020. godine na definiranje opterećenja (hidrauličkog i biološkog) uređaja za pročišćavanje otpadnih voda.In order to supress the COVID-19 global pandemics in 2020, strict measures, which limited numerous activities and movement of people at the global level, including Croatia, were introduced. The paper analyses the impact of introduced limitations on the water demand per individual consumer categories (households, economy) based on data collected for 17 water services providers in the Republic of Croatia. The data for the continental and coastal (tourism-oriented) parts of the country were equally represented. The conducted analysis looked at water consumption in 2020 in relation to average consumption values in the previous 5-year period. The changes regarding the shares of individual categories in the total consumption were detected, and conclusions and recommendations were offered in relation to the need for gaining a critical insight into the 2020 data when developing projections within the water demand analysis. An indicative example was also used as a demonstration of the impact of changes in the 2020 water consumption on the determination of (hydraulic and biological) loads on waste water treatment plants.Im Laufe des Jahres 2020 wurden strenge Maßnahmen getroffen, die zahlreiche Aktivitäten, Tätigkeiten und Bewegungsfreiheit der Bevölkerung in der ganzen Welt und so auch in Kroatien beschränkt haben mit dem Ziel, die COVID-19-Pandemie zu bekämpfen. In diesem Beitrag wird der Einfluss der eingeführten Beschränkungen auf den Wasserverbrauch in einzelnen Verbraucherkategorien (Haushalte, Industrie) analysiert auf Grund der Angaben, die von 17 Wasserversorgern in Kroatien erhoben wurden. Dabei werden die Angaben für das kontinentale Gebiet (nicht-touristisch orientiert) und die Küste (touristisch orientiert) gleichermaßen vertreten. Die Analyse des Wasserverbrauchs im Jahre 2020 wurde in Vergleich zu den durchschnittlichen Werten im vergangenen Fünfjahreszeitraum durchgeführt. Es konnten Änderungen in Bezug auf den Anteil einzelner Kategorie im Gesamtverbrauch festgestellt werden. Die Ergebnisse und Empfehlungen für die Notwendigkeit einer kritischen Betrachtung dieser Angaben für 2020 werden angesichts der Erfassung von Projektionen im Rahmen der Wasserbedarfsanalysen gegeben. Auf einem Beispiel wird auch der Einfluss der Änderungen im Wasserverbrauch in 2020 auf die Bestimmung der hydraulischen und biologischen Belastung einer Abwasserkläranlage dargestellt